1. Field
Aspects of this disclosure relate to a negative active material for a rechargeable lithium battery, a method of manufacturing the same, and a rechargeable lithium battery including the same.
2. Description of the Related Technology
Lithium rechargeable batteries have recently drawn attention as power sources for small portable electronic devices. Since they use an organic electrolyte solution, they have twice the discharge voltage of conventional batteries using an alkali aqueous solution, and accordingly have high energy density.
As for positive active materials for a rechargeable lithium battery, lithium-transition element composite oxides being capable of intercalating lithium such as LiCoO2, LiMn2O4, LiNi1-xCOxO2 (0<x<1), and so on have been researched.
As for negative active materials for a rechargeable lithium battery, various carbon-based materials such as artificial graphite, natural graphite and hard carbon, which can all intercalate and deintercalate lithium ions, a metal-based material such as Si and the like, or a lithium composite compound such as lithium vanadium oxide have been used.
Herein, soft carbon refers to a carbon material that can be converted into the crystal structure of graphite, while hard carbon refers to a carbon material that cannot be converted into the crystal structure of graphite. In general, since soft carbon is prepared from residues remaining after treatment of petroleum charcoal, soft carbon costs relatively less than hard carbon, while since hard carbon is prepared by heat-treating a resin-based polymer, hard carbon tends to cost more. Soft carbon is more likely to be converted into graphite than hard carbon. and thus has relatively higher crystallinity than hard carbon.
Since graphite has high crystallinity and thus large capacity but small openings in the crystal lattice where lithium ions can enter, and thus high resistance against the ions, graphite may not be good for high input or output. On the other hand, carbons have low crystallinity, and so have small and largely non-reversible capacity. However, the carbons have large edges where ions can rapidly come in and go out, and therefore hard carbons can exhibit high input and output.